DESCRIPTION: This proposal concerns cognitive impairment in children with neurofibromatosis 1 (NF1), a common autosomal-dominant genetic disease that is associated with central nervous system involvement and that has cognitive impairment as the most common neurological symptom. Few children are retarded but 40 percent have learning disabilities. In the last decade, the NF1 gene has been localized and sequenced. Its protein products may stimulate GAPs (GTPase activating proteins), that affect other proteins important for cell proliferation and development. The rationale for the proposed research is that the type and etiology of the learning disabilities in NF1 are poorly understood. The general objective is to determine whether the cognitive impairments are one component of a failure of control of brain growth and development. The study is designed to provide data about normal brain growth and the growth pattern of NF1 children and will allow correlations between phenotype and genotype for the learning disabilities in NF1.